A Baltimore police officer awaiting trial for murder in the death of his fiancee died early Monday in an apparent suicide in jail, state prison officials said.

James Walton Smith, 49, was being held in protective custody in the state's high-rise jail complex at Madison Street and Greenmount Avenue, officials said.

The death brings more scrutiny to the embattled state corrections system, which pledged reforms after the April indictment of an inmate federal prosecutors say conspired with 13 corrections officers in the Baltimore City Detention Center to smuggle in drugs and cellphones.

On Monday, prison officials said an officer doing routine rounds about 1 a.m. at the Maryland Reception, Diagnostic, and Classification Center found Smith unresponsive in his cell.

Smith had been moved from Central Booking and was being housed alone. He was not on suicide watch, corrections spokesman Mark Vernarelli said.

Medical personnel at the jail tried to revive Smith, officials said, but were unsuccessful. He was pronounced dead at John Hopkins Hospital.

"His family is extremely distraught," said Janice Bledsoe, one of Smith's defense attorneys. "His family was extremely supportive of him."

The Internal Investigative Unit of the Maryland Department of Public Safety and Correctional Services is investigating, prison officials said in a statement.

Officials released few details on Smith's death on Monday. The Office of the Chief Medical Examiner said an autopsy was being performed to determine the cause and manner of death.

Jail officials say they have made strides over the past five years in preventing suicides, with better psychological training and risk-assessment tools.

Vernarelli said inmates who are trained as "suicide prevention observers" monitor at-risk detainees around the clock.

Smith, a 20-year Baltimore police veteran assigned to the motorcade unit, was charged with fatally shooting his fiancee, Kendra Diggs, 37, in May after a domestic dispute turned into a nearly six-hour barricade and standoff at the couple's West Baltimore home.

Two Baltimore police officers were dispatched to Smith and Diggs' home in the 1100 block of N. Parrish St. on May 7 after a neighbor reported a domestic disturbance.

When the officers arrived, police say, they heard Diggs inside calling for help. After no one responded to their knocks, the officers kicked in the door and brought Diggs outside.

The officers say they asked Smith, who was off duty at the time, to come outside to talk. They say he ran upstairs.

Diggs was standing on the sidewalk with an officer when police say Smith fired a shot from his second-floor window that struck her in the head.

Smith barricaded himself in the home for nearly six hours with the couple's 4-year-old son while a tactical team retrieved Diggs' body and negotiators urged Smith to surrender.

Smith released the boy and surrendered peacefully just after 9 p.m. Police say he expressed remorse upon arrest.

Three suicides have been reported in state correctional facilities this year, Vernarelli said. According to Maryland prison statistics, five inmates or detainees committed suicide in 2012, down from 16 in 2007. Vernarelli attributed the drop to better training and practices.

Thomas W. White, who served as chief psychologist at facilities including the federal penitentiary in Leavenworth, Kan., said it's common for jailed law enforcement officers to be given a single cell and held in protective custody, given the acrimony they face from other criminal suspects.

White said it can be difficult to stop inmates who are not on suicide watch from killing themselves.

Not all suicidal detainees show warning signs or project their intentions to jail staff, he said. Reasons inmates decide to take their own lives are as varied as those of anyone on the outside, he said, but detainees face stresses that can include inmate harassment, bad news from a lawyer and looming trials or sentences.

"If somebody decided 'I don't want to live anymore' for any reason, it can be very difficult to prevent that because they may not exhibit the warning signs of someone with depression," White said. "Just because someone dies does not always mean that somebody is culpable."

Smith was scheduled for a jury trial Aug. 30 on charges of first-degree murder and use of a firearm in a felony or violent crime.

The World Health Organization reported in 2007 that pretrial detainees are more likely to commit suicide closer to court appearances — especially when they anticipate a guilty verdict and a harsh sentence.

Pretrial detainees are 71/2 times more likely to commit suicide than men who are not incarcerated, the organization reported.

Police have said Smith had no history of domestic abuse and was a respected member of the Police Department with broad experience that included tactical operations. He was honorably discharged from the Army in 1992.

"James Smith's death brings to a close a sad and final chapter in a series of tragic events that left four children without parents," the Police Department said in a statement. "The collective thoughts and prayers of the Baltimore Police Department go out to everyone involved."